Trigger circuit for use with multivibrators

ABSTRACT

A monostable multivibrator including trigger circuitry therefor comprising monostable multivibrator means having a normally conducting control element and a normally non-conducting control element, trigger means including means responsive to the positive-going transitions in an input signal for controlling at least one of said control elements to switch the monostable multivibrator means to its unstable state for a predetermined length of time; and the trigger means including means responsive to the negative-going transitions in the input signal for controlling the other of the control elements to again switch the monostable multivibrator to its unstable state for the predetermined length of time; whereby the circuitry may multiply the frequency of the input signal at the output of the monostable multivibrator means.

United States Patent 1191 Tanimoto Nov. 5, 1974 TRIGGER CIRCUIT FOR USEWITH 3,705,991 12/1972 Hobo 307/273 MULTIVIBRATORS 3,727,082 4/1973Codina 307/273 [76] Inventor: Kenji Tanimoto, 3-5, Akasaka PrimaryExammer-John S. Heyman 3 chome Mmatoku Tokyo Japan Attorney, Agent, orFirm-J. T. Martin; Gerald J. [22] Filed: Dec. 20, 1972 Ferguson, Jr.;Joseph J. Baker [21] Appl. No.: 316,752

[57] ABSTRACT [30] Foreign Application Priority Data A monostablemultivibrator including trigger circuitry Dec. 23, 1971 Japan 46-104091therefor Comprising monostable multivibrator moans having a normallyconducting control element and a [52] US. Cl. 307/273, 328/20, 328/127,n rm y non-conducting control l rigg r 307/236 means including meansresponsive to the positive- [51] Int. Cl. H0311 3/284 g i g i io s in aninput signal for Controlling at [58] Field of Search 307/273, 292, 236;least one of d ntr l lements t switch the mono- 328/207, 20, 127 stablemultivibrator means to its unstable state for a predetermined length oftime; and the trigger means 5 R f r Cit d including means responsive tothe negative-going tran- UNITED STATES PATENTS sitions in the inputsignal for controlling the other of 307 273 the control elements toagain switch the monostable 2; 3074273 multivibrator to its unstablestate for the predeter- 339l389 7/1968 a g 307,273 mined length of time;whereby the circuitry may mul- 3144311 18 5/1969 R0gr5::::::::::i:....111:: 307/273 p y the frequency o t input Signal at the Output of3,483,479 12/1969 Harshbarger 307/273 tho monostablo multlvlbratormoans- 3,57l,732 3/l97i Richardson 307/273 3,643,159 2/1972 Seki 307/27349%.?! 3 KQYEPAELAFEFS,

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(PRIOR ART) B CH Di l '1 HM MONO- ,Jl[L[L[L f :ATUASIIE fo FIG. 3

m L r L TRIGGER CIRCUIT FOR USE WITH MULTIVIBRATORS CROSS REFERENCES TORELATED APPLICATIONS This application is related to copendingapplication, entitled Frequency Multiplying Circuit, and filed herewithby the inventor of the subject application. The above copendingapplication is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to triggering circuitry for multivibrators and in particular tosuch circuitry using triggering pulses of alternating polarities forone-shot multivibrators.

2. Description of the Prior Art FIG. 1 is an illustrative block diagramof a conventional multivibrator including the triggering circuitrytherefor. Input pulse train f,, is applied to a differentiator circuit awhich generates spikes of alternating polarities. These are applied to aphase inverter circuit b which produces the triggering pulses for aone-shot multivibrator c all with the same polarity. The output pulsetrain from the multivibrator has double the frequency of the input pulsetrain.

SUMMARY OF THE INVENTION An object of the invention is to providetriggering pulses of alternating polarity which can directly be appliedfrom a differentiator to trigger one-shot multivibrators.

It is a further object of this invention to provide a simple and stabletriggering circuit for multivibrators through the elimination of phaseinverter circuitry and the like.

Other objects and advantages of this invention will become apparent uponreading the appended claims in conjunction with the following detaileddescription and the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an illustrative block diagramof conventional circuits.

FIG. 2 is an illustrative schematic diagram of triggering circuit andmultivibrator in accordance with the invention.

FIG. 3 illustrates waveforms occurring in the FIG. 2 embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is now describedin detail by way of the embodiment of FIG. 2. When the input terminal Eis not energized, one of the semiconductor devices Q remains cutoff,while the other device Q remains conductive. The pulse train of FIG. 3ais applied to the input terminal E, and differentiated by capacitor Cand resistor R, to generate the triggering spikes of alternatingpolarities shown in FIG. 3b.

The instant the positive spike reaches the base of Q1 through thecapacitor C and the forward biased diode CR the device Q, is turned onto its conductive state, thereby causing the collector voltage of Q. todecrease fron an initial positive value, thus, reducing the voltagecoupled to the base of O to cut off FIG. 30 shows the change in thecollector voltage of 02 where the pulse width is determined by thephysical values of the discharging circuit elements, C and R After thetime lapse corresponding to the pulse width, 0 returns to its originalconductive state.

The negative spike is coupled through the capacitor C and the forwardbiased diode CR to the base of Q and sets 0 from the conductive to thecutoff state, consequently causing the collector voltage of O to rise inthe positive direction. Due to the collector voltage of 0 beingconnected to the base of Q through the feed-back resistor R thecollector voltage of 0 decreases as shown in FIG. 3d, with the resultantchange in the state of Q from conductive to cutoff state. As statedabove, Q returns to the stable state of conduction after the time lapseequal to the time constant determined by C and R From the foregoing, itcan be seen that by using the exemplary circuit of FIG. 2, a pulse trainhaving a frequency twice that of the input pulse train is available atthe output terminal E Numerous modifications of the invention willbecome apparent to one of ordinary skill in the art upon reading theforegoing disclosure. During such a reading, it will be evident thatthis invention provides unique multivibrator and trigger circuittherefor for accomplishing the objects and advantages hereinstated.

What is claimed is:

l. A monostable multivibrator including trigger circuit thereforcomprising:

a single monostable multivibrator means having a normally conductingtransistor with a collector, emitter, and base and a normallynon-conducting transistor with a collector, emitter, and base;

trigger means including means responsive to the positive-goingtransitions in an input pulse signal for triggering said normallynon-conducting transistor on to thereby switch said monostablemultivibrator means to its unstable state for a predetermined length oftime which is set to be always shorter in duration than said inputsignal; and

said trigger means including means responsive to the negative-goingtransitions in said input pulse signal for triggering said normallyconducting transistor off to thereby again switch said monostablemultivibrator to its unstable state for said predetermined length oftime,

said input signal being a pulse train and said trigger means includingmeans for differentiating said input pulse train so that positive spikesare produced for each positive-going transition in the pulse train andapplied to said one transistor and negative spikes are produced for thenegativegoing transitions and applied to said other transistor,

said trigger means further including a first diode having one poleconnected to said differentiating means and its other pole directlyconnected to the base of said normally non-conducting transistor and asecond diode having one pole connected to said differentiating means andits other pole directly connected to the base of said normallyconducting transistor, both said diodes being connected to theirrespective transistors at the same time.

2. A multivibrator as in claim 1 wherein said positive spikes areapplied to the normally non-conducting tranbetween the collector of thenormally non-conducting transistor and the base of the normallyconducting transistor and a resistor connected between the bias voltagesupplied for said multivibrator and the base of said normally conductingtransistor whereby said capacitor discharges through said resistor toestablish said predetermined time whenever either said normallyconducting transistor is turned off or said normally non-conductingtransistor is turned on.

1. A monostable multivibrator including trigger circuit thereforcomprising: a single monostable multivibrator means having a normallyconducting transistor with a collector, emitter, and base and a normallynon-conducting transistor with a collector, emitter, and base; triggermeans including means responsive to the positive-going transitions in aninput pulse signal for triggering said normally non-conductingtransistor on to thereby switch said monostable multivibrator means toits unstable state for a predetermined length of time which is set to bealways shorter in duration than said input signal; and said triggermeans including means responsive to the negativegoing transitions insaid input pulse signal for triggering said normally conductingtransistor off to thereby again switch said monostable multivibrator toits unstable state for said predetermined length of time, said inputsignal being a pulse train and said trigger means including means fordifferentiating said input pulse train so that positive spikes areproduced for each positive-going transition in the pulse train andapplied to said one transistor and negative spikes are produced for thenegativegoing transitions and applied to said other transistor, saidtrigger means further including a first diode having one pole connectedto said differentiating means and its other pole directly connected tothe base of said normally non-conducting transistor and a second diodehaving one pole connected to said differentiating means and its otherpole directly connected to the base of said normally conductingtransistor, both said diodes being connected to their respectivetransistors at the same time.
 2. A multivibrator as in claim 1 whereinsaid positive spikes are applied to the normally non-conductingtransistor to turn it on and said negative spikes are applied to saidnormally conducting transistor to turn it off.
 3. A multivibrator as inclaim 1 where said control elements are NPN transistors and the negativepole of said first diode is directly connected to the base of saidnormally non-conducting transistor and the positive pole of said seconddiode is directly connected to the base of said normally conductingtransistor.
 4. A multivibrator as in claim 3 where said monostablemultivibrator means includes a capacitor connected between the collectorof the normally non-conducting transistor and the base of the normallyconducting transistor and a resistor connected between the bias voltagesupplied for said multivibrator and the base of said normally conductingtransistor whereby said capacitor discharges through said resistor toestablish said predetermined time whenever either said normallyconducting transistor is turned off or said normally non-conductingtransistor is turned on.